US President Barack Obama has publicly joked about Area 51 at a White House event for the Kennedy Center honorees.

"Now, when you first become president, one of the questions that people ask you is, what's really going on in Area 51?" he said.

"When I wanted to know, I'd call Shirley MacLaine. I think I just became the first president to ever publicly mention Area 51. How's that, Shirley?"

MacLaine, who is among five artists who are receiving the honour, has claimed to have seen UFOs.

She was joined by Billy Joel joins Carlos Santana, Herbie Hancock and opera star Martina Arroyo at the event, where they were awarded the nation's highest honour for influencing American culture through the arts.

"This is different. It's our nation's capital," he told The Associated Press. "This is coming more from my country than just people who come to see me. It's a little overwhelming."

The 64-year-old musician born in the Bronx has been playing the piano since he was a boy, growing up on New York's Long Island. There was always music in the house, he said. His mother sang. His father played the piano.

Mr Obama saluted the honorees, saying the performers were extraordinary.

"The diverse group of extraordinary individuals we honour today haven't just proven themselves to be the best of the best," Mr Obama said. "Despite all their success, all their fame, they've remained true to themselves - and inspired the rest of us to do the same."

But it was his remarks about Area 51 that made the news in the US.

Conspiracy theorists have long been obsessed by the secret Nevada base and have alleged it was a location of frequent UFO sightings.

Area 51 had been rumored to be a Central Intelligence Agency facility, but new documents released in August confirmed its existence.